Is it possible to hide class methods when the class has not been properly instantiated?

[ahaupt]

Hi all,

Do you know if it is possible to hide class methods when the class has
not been "properly" instantiated?

Say in the following example, I'd like to hide or disable Drive() when
the numWheels == 0.

class Car
{

int _numWheels;

Car()
{
_numWheels = 0;
}

Car(int numWheels)
{
_numWheels = numWheels;
}

void Drive() {...}
}

I don't suppose there's a way to do it, other than checking numWheels >
0 in each class method.

What's the proper way to do this? How do you guys handle this
situation?

Thanks,
Andre

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

No, there is no way of doing that, you will have to check your
preconditions in each method.

Now in your case, you could check in the constructor if numWheels is > 0 ,
if not throw an exception

you could do the same if you have a property allowing to change the member
variable.
cheers,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation
<ah****@gmail.com> wrote in message
news:11**********************@g43g2000cwa.googlegr oups.com...

Hi all,

Do you know if it is possible to hide class methods when the class has
not been "properly" instantiated?

Say in the following example, I'd like to hide or disable Drive() when
the numWheels == 0.

class Car
{

int _numWheels;

Car()
{
_numWheels = 0;
}

Car(int numWheels)
{
_numWheels = numWheels;
}

void Drive() {...}
}

I don't suppose there's a way to do it, other than checking numWheels >
0 in each class method.

What's the proper way to do this? How do you guys handle this
situation?

Thanks,
Andre

[ahaupt]

Hi Ignacio,

Great suggestion!

That's just what I'm after.

Thanks for that,
Andre

[Joanna Carter \(TeamB\)]

<ah****@gmail.com> a écrit dans le message de news:
11**********************@g43g2000cwa.googlegroups. com...

Hi all,

Do you know if it is possible to hide class methods when the class has
not been "properly" instantiated?

Say in the following example, I'd like to hide or disable Drive() when
the numWheels == 0.
Simply hide the default constructor :
class Car
{

int _numWheels;

private Car()
{
_numWheels = 0;
}

public Car(int numWheels)
{
_numWheels = numWheels;
}

public void Drive() {...}
}

Then it is impossible to construct a valid instance without passing a number
to the parameterised constructor.

Joanna

--
Joanna Carter
Consultant Software Engineer

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

Or just remove it, most probably it has no use at all
cheers,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation

"Joanna Carter (TeamB)" <jo*****@nospamforme.com> wrote in message
news:e3**************@TK2MSFTNGP09.phx.gbl...

<ah****@gmail.com> a écrit dans le message de news:
11**********************@g43g2000cwa.googlegroups. com...

Hi all,

Do you know if it is possible to hide class methods when the class has
not been "properly" instantiated?

Say in the following example, I'd like to hide or disable Drive() when
the numWheels == 0.

Simply hide the default constructor :

class Car
{

int _numWheels;

private Car()
{
_numWheels = 0;
}

public Car(int numWheels)
{
_numWheels = numWheels;
}

public void Drive() {...}
}

Then it is impossible to construct a valid instance without passing a
number
to the parameterised constructor.

Joanna

--
Joanna Carter
Consultant Software Engineer

[Jeff Louie]

As suggested, you can make it impossible to construct an invalid object
or you
can provide an isValid() method or flag.

Regards,
Jeff

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